Our goal is to develop a low cost therapy for hepatocellular carcinoma (HCC), an important worldwide cause of cancer-related death with over 500,000 cases diagnosed each year. 5-year survival rates are less than 12%, and there is an urgent need for effective therapies. Risk factors include chronic hepatitis viral infections, cirrhosis of any cause, and non-alcoholic steatohepatitis (NASH). Because the highest burden is in developing countries, low cost technologies are especially needed. Using a validated mouse model of NASH-related HCC in which 100% of mice develop HCC after streptozotocin injection followed by high fat diet, we recently discovered that treatment of these mice with clemizole-a first generation anti-histamine we found to be highly concentrated in liver-led to a dramatic 10-fold reduction in the incidence and size of HCC nodules, with 2/3 mice having undetectable lesions. Moreover, clemizole is safe and well tolerated at comparable doses in humans, including in our recent studies in patients with hepatitis C. Finally, the concentration of clemizoe expected to be achieved in patient livers is highly toxic to human HCC cells in culture, whereas it is well tolerated by primary human liver cells. We now wish to translate these exciting data int a new low cost therapy for HCC by: 1) Synthesizing and determining the relative cytotoxicity against a variety of HCC cell lines (mouse and human) of clemizole vs. its major metabolites (M1 and M12) and selected analogs; 2) Determining the therapeutic potential, in addition to chemoprevention, of clemizole (and any identified back up molecule) against HCC by identifying new HCC lesions in streptozotocin/ high fat diet mice by CT scan prior to treatment; and determining the change in lesion size, and rate of new lesion formation, as a function of subsequent treatment with clemizole (vs. potential back up) vs. vehicle control; and 3) Determining the mechanism of clemizole's toxicity to HCC by a) characterizing the nature of HCC toxicity (apoptosis vs. necrosis vs. autophagy); b) determining the role of clemizole's antihistamine activity (by analyzing the HCC toxicity of a collection of antihistamines and clemizole analogs devoid of clemizole's tertiary amine); and c) performing a genome-wide high density shRNA screen in clemizole-treated HCC cell lines to identify candidate target gene(s). Successful accomplishment of our aims will yield in vivo proof-of-concept for the intended clinical indication in an appropriate validated model, as well as a mechanism for clemizole's dramatic in vivo anti-HCC activity. Importantly, our team is highly experienced in successful drug discovery and development and has the unique experience and expertise to translate our compelling preliminary data into a clinic-ready therapy for the devastating disease of hepatocellular carcinoma, with an exciting commercial development plan.